code: def testRegretMetric(self, metric_class, fn, expected_result):
      traj = self._create_trajectory()
      metric = metric_class(fn)
      self.evaluate(metric.init_variables())
      traj_out = metric(traj)
      deps = tf.nest.flatten(traj_out)
      with tf.control_dependencies(deps):
          result = metric.result()
      result_ = self.evaluate(result)
      self.assertEqual(result_, expected_result)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import tensorflow
  from tf_agents.bandits.metrics import tf_metrics
  from tf_agents.bandits.policies import constraints
  from tf_agents.specs import tensor_spec
  from tf_agents.trajectories import time_step
  from tf_agents.trajectories import trajectory
label_desc: Use image node_id 6 for calling the TFMetricsTest obj's underlying member method code with example usage: obj.testRegretMetric(metric_class, fn, expected_result) without return types